GAO-20-584SP 1 (2020-05-20)

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                           Science, Technology Assessment,
G       A      O         Iand Analytics



What is it? There are currently three types of tests for COVID-19:
molecular, antigen, and serology. Molecular tests and a new antigen
test help diagnose active COVID-19 infections, and serology tests
help determine whether someone was previously exposed to the novel
coronavirus, which causes COVID-19.

How does it work? While each kind of test takes a different approach,
they all collect vital information about exposure to the virus.

Molecular tests amplify and detect genetic material from novel coronavirus
in a sample taken from a patient's saliva, nose, or throat to determine
whether there is an active infection (fig. 1). For example, molecular tests
based on the polymerase chain reaction (PCR) use a genetic photocopier,
copying a unique portion of the coronavirus genetic material, if present,
until there are enough copies to detect.

Antigen tests can detect the virus by binding parts of the virus, called
antigens, to a membrane. Antibodies that can fluoresce are also added to
the membrane. If enough antigen is present to bind to the antibodies, the
total fluorescence from the antibodies becomes high enough to indicate a
positive result.

Serology tests, which typically require a sample of blood from a patient,
can detect the presence of antibodies produced by a patient's immune
system in response to the coronavirus (fig. 1). Such antibodies can persist
in the blood after a patient recovers from an infection. Thus, a positive
serology test result indicates prior exposure to the novel coronavirus but
does not necessarily mean that the patient is still infected.






Viral genetic
Source: GAO. I GAO-20-584

   Detect     Antibodies



       Most Common COVID-19 Test Types. Molecular tests detect viral genetic
material. Serology tests detect antibodies against the virus.

How mature is it? All three kinds of COVID-19 tests are commercially
available under the Food and Drug Administration's (FDA's) emergency
use authorization (EUA), which allows for the use of certain unapproved
medical products or unapproved uses of approved medical products
under certain circumstances during a public health emergency. As of May
13, 2020, FDA has authorized at least 56 molecular tests for COVID-19
via EUA; these tests generally rely on PCR technology. Devices used
for administering molecular tests range in size from larger equipment to
smaller, portable devices that can be used on-site near the patient.

On May 8, 2020, FDA authorized the first antigen test for COVI D-1 9 via
EUA. According to FDA, antigen tests, which can be run in minutes, have
a higher chance of false negatives compared to molecular tests. FDA
states that negative antigen test results may need to be confirmed with a
molecular test before making treatment decisions.

As of May 13, 2020, FDA has authorized at least 12 serology tests for
COVID-19 via EUA. For COVID-19, serology tests were first authorized by
FDA about a month after molecular tests were authorized. Devices used to
administer serology tests also range in size, with some about the size of an
over-the-counter pregnancy test.

Testing provides critical information for a variety of purposes, including
medical care, policymaking, and business. For example:

  Determining risk. Serology tests can help establish the percentage
     of the population previously exposed to the virus. Such information
     can help improve the accuracy of statistics on infection rates, among
     other things.

  Understanding disease impact. Testing can help establish the
     impact of the disease, including identifying those who may have
     been exposed to the virus but did not show symptoms and those
     who recovered. This is important for characterizing the risk of the
     disease to the elderly and other subpopulations.

  Guiding treatment and resource allocation. Molecular and antigen
     tests can provide information on the rate and geographic location of
     active infections. This can help guide patient treatment and inform
     decisions about the distribution of medical supplies and equipment.

  Informing responses. Testing is also important for informing
     decisions on quarantine and isolation, including decisions related
     to health care workers. Additionally, testing can help inform public
     responses such as school closures and reopenings.

GAO-20-584SP COVID-19 Testing


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